The present invention relates, in general, to the field of continuous operation membrane compartmentalized biological reactors, and in particular, to a new and useful symmetrical operation reactor which automatically prevents concentration polarization and deposition layer formation (or fouling) on membrane surfaces and provides for gentle agitation of fragile particles.
In multi-phase flow biological or chemical reactor processes, certain constitutents have to be permanently separated from the mainstream solution while constantly being mixed. For example in bioreactors, enzymes, tissue cultures, or whole cells are entrapped in specific reactor compartments and gently agitated. Membranes of all types and shapes together with a variety of mixing devices have been utilized in modern reactor design in an attempt to achieve these goals. However, all membrane-moderated reactors suffer from concentration polarization and membrane fouling which in turn may cause flux reduction, higher energy expenditure, transients, membrane failure and/or disruption of the continuous process since at one point membrane cleaning by some physical or chemical means, is required. In addition, conventional mixing (e.g. with a stirrer) may cause mechanical destruction of the microorganisms. Until the membrane fouling problem is solved, the performance of membrane-moderated continuous flow reactors will be technically and economically inferior to conventional reactors such as stirred tanks with recycling or bubble columns.
With respect to biochemical reactors, a number of reactors using membranes to separate (or entrap) biocatalysts but allow nutrients to pass freely, are known. Some approaches to utilizing microorganisms to produce a product include the structure disclosed in U.S. Pat. No. 3,186,917 to Gerhard et al. A membrane is provided to pass a nutrient solution to a culture of microorganisms for producing a desired product.
U.S. Pat. No. 3,734,851 to Matsumura describes the use of two membranes with cells being maintained therebetween with flow of mass to and from the cells being accomplished through the respective membrane. U.S. Pat. No. 3,769,176 to Hise et al discloses the production of biochemicals by microorganisms and the like, wherein nutrients are supplied to the microorganisms and removed from the microorganisms by means of membranes. The following U.S. patents also describe these membranes in similar environments: U.S. Pat. No. 3,281,087 to Knazek et al; U.S. Pat. No. 3,915,802 to Kominek; amd U.S. Pat. No. 4,241,187 to White.
Designs and operational modes for innovative membrane chamber bioreactors which are of particular interest for the application of the present invention have recently been described in the article "Membrane Technology and Biotechnology", (1980) by A. S. Michaels, pp. 329-351, printed in the Netherlands by Elsevier Scientific Publishing Co., Amsterdam.